/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.feilong.lib.net.io;

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;

/***
 * This class wraps an output stream, replacing all singly occurring
 * &lt;LF&gt; (linefeed) characters with &lt;CR&gt;&lt;LF&gt; (carriage return
 * followed by linefeed), which is the NETASCII standard for representing
 * a newline.
 * You would use this class to implement ASCII file transfers requiring
 * conversion to NETASCII.
 *
 *
 ***/

public final class ToNetASCIIOutputStream extends FilterOutputStream{

    private boolean __lastWasCR;

    /***
     * Creates a ToNetASCIIOutputStream instance that wraps an existing
     * OutputStream.
     *
     * @param output
     *            The OutputStream to wrap.
     ***/
    public ToNetASCIIOutputStream(OutputStream output){
        super(output);
        __lastWasCR = false;
    }

    /***
     * Writes a byte to the stream. Note that a call to this method
     * may result in multiple writes to the underlying input stream in order
     * to convert naked newlines to NETASCII line separators.
     * This is transparent to the programmer and is only mentioned for
     * completeness.
     *
     * @param ch
     *            The byte to write.
     * @throws IOException
     *             If an error occurs while writing to the underlying
     *             stream.
     ***/
    @Override
    public synchronized void write(int ch) throws IOException{
        switch (ch) {
            case '\r':
                __lastWasCR = true;
                out.write('\r');
                return;
            case '\n':
                if (!__lastWasCR){
                    out.write('\r');
                }
                //$FALL-THROUGH$
            default:
                __lastWasCR = false;
                out.write(ch);
                return;
        }
    }

    /***
     * Writes a byte array to the stream.
     *
     * @param buffer
     *            The byte array to write.
     * @throws IOException
     *             If an error occurs while writing to the underlying
     *             stream.
     ***/
    @Override
    public synchronized void write(byte buffer[]) throws IOException{
        write(buffer, 0, buffer.length);
    }

    /***
     * Writes a number of bytes from a byte array to the stream starting from
     * a given offset.
     *
     * @param buffer
     *            The byte array to write.
     * @param offset
     *            The offset into the array at which to start copying data.
     * @param length
     *            The number of bytes to write.
     * @throws IOException
     *             If an error occurs while writing to the underlying
     *             stream.
     ***/
    @Override
    public synchronized void write(byte buffer[],int offset,int length) throws IOException{
        while (length-- > 0){
            write(buffer[offset++]);
        }
    }

}
